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CVE Record

CVE-2023-54195: rxrpc: Fix timeout of a call that hasn't yet been granted a channel

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix timeout of a call that hasn't yet been granted a channel afs_make_call() calls rxrpc_kernel_begin_call() to begin a call (which may get stalled in the background waiting for a connection to become available); it then calls rxrpc_kernel_set_max_life() to set the timeouts - but that starts the call timer so the call timer might then expire before we get a connection assigned - leading to the following oops if the call stalled: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... CPU: 1 PID: 5111 Comm: krxrpcio/0 Not tainted 6.3.0-rc7-build3+ #701 RIP: 0010:rxrpc_alloc_txbuf+0xc0/0x157 ... Call Trace: <TASK> rxrpc_send_ACK+0x50/0x13b rxrpc_input_call_event+0x16a/0x67d rxrpc_io_thread+0x1b6/0x45f ? _raw_spin_unlock_irqrestore+0x1f/0x35 ? rxrpc_input_packet+0x519/0x519 kthread+0xe7/0xef ? kthread_complete_and_exit+0x1b/0x1b ret_from_fork+0x22/0x30 Fix this by noting the timeouts in struct rxrpc_call when the call is created. The timer will be started when the first packet is transmitted. It shouldn't be possible to trigger this directly from userspace through AF_RXRPC as sendmsg() will return EBUSY if the call is in the waiting-for-conn state if it dropped out of the wait due to a signal.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2023-54195 is a Linux kernel rxrpc timing bug that can cause a kernel NULL pointer crash when an AFS call waits too long for a channel. The sources indicate system stability risk, not data theft or code execution. Direct triggering from userspace is described as unlikely through AF_RXRPC.

Executive priority

Treat as a targeted stability risk for Linux infrastructure using AFS/rxrpc, not an emergency internet-wide exposure based on current evidence. Patch through normal kernel maintenance, faster where affected functionality is used or uptime is critical.

Technical view

afs_make_call() starts an rxrpc call, then rxrpc_kernel_set_max_life() starts the call timer before a connection channel is assigned. If the call stalls, timer expiry can reach rxrpc_alloc_txbuf() through ACK/event handling and dereference NULL. The fix records timeouts at call creation and starts the timer when the first packet is transmitted.

Likely exposure

Exposure is most relevant to Linux systems using rxrpc/AFS paths. The source bundle lists Linux versions including 6.2, 6.2.16, 6.3.3, and 6.4 as affected, but exact distribution package status requires vendor confirmation.

Exploitation context

The CVE is not in KEV and the supplied sources do not report active exploitation. The kernel note says direct userspace triggering through AF_RXRPC should not be possible because sendmsg() returns EBUSY in the waiting-for-connection state after signal interruption.

Researcher notes

The evidence supports a race/timer ordering flaw leading to kernel oops. The source explicitly limits direct AF_RXRPC userspace triggerability. No CVSS, CWE, proof of exploitation, or distribution-specific fix matrix is provided in the bundle.

Mitigation direction

  • Review kernel vendor advisories for CVE-2023-54195 package status.
  • Update to a kernel containing the referenced stable fixes.
  • Prioritize systems using AFS or rxrpc functionality.
  • Monitor kernel logs for rxrpc-related oops or NULL dereference events.

Validation and detection

  • Inventory Linux kernel versions across affected fleets.
  • Check whether rxrpc or AFS functionality is enabled or in use.
  • Confirm vendor kernels include the referenced stable commits.
  • Review crash logs for rxrpc_alloc_txbuf or rxrpc_input_call_event traces.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux9d35d880e0e4a3ab32d8c12f9e4d76198aadd42d, 9d35d880e0e4a3ab32d8c12f9e4d76198aadd42d, 9d35d880e0e4a3ab32d8c12f9e4d76198aadd42dunaffected
LinuxLinux6.2, 0, 6.2.16, 6.3.3, 6.4affected
Weakness

CWE details

No CWE listed

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